Thread cutter for buttonhole sewing machines



J. H. PIKUL ET AL THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Jan 19, 1937.

5 Sheets-Sheet l InverwToT-s Filed Nov. 15, 1953 G Q WA FM 0 0 0 Jan. 19, 1937.

J. H. PlKUL ET AL THREAD CUTTER FOR BUTTONHQLE SEWING MACHINES Filed NOV. 15, 1953 5 Sheets-Sheet r r A Y InvenTors.

, doseph I-LPIKUI Carl A.O.Grip

\ M Mx M ATTy s.

Jan. 19, 1937. J. H. PlKUL ET AL THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Filed Nov. 15, 1933 5 Sheets-Sheet 3 Fig. 4.

ATTys:

mm Pr nD| .I|& 3 w l wmw w w uc y 9 83 3 w m 6 a" .3 Q m F E a Jan. 19, 1937. J. PlKUL ET AL 2,068,509

THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Filed Nov. 15, 1953' 5Sheets-Shee1; 4

lnvenTors. Joseph H. PI KUI Carl AD; Grip bymMEW ATTys.

' Jan. 19, 1937 I K ET AL 2,068,509

THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Filed NOV. 15, 1933 5 Sheets-Sheet 5 lnvehi'ors.

doseph H. PiKul Cdrl A.O.Grip

ATTy s.

Patented Jan. 19, 1937 UNITED STATES PATENT OFFICE THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES corporation of Maine Application November 15, 1933, Serial No. 698,128

32 Claims. (01. 112-252) This invention relates to thread-trimming devices for buttonhole sewing machines by which the thread or threads leading from the under side of the work at the completion of the buttonhole are cut or trimmed after the clamps have been opened.

Some buttonhole sewing machines are constructed so that after the sewing on the buttonhole has been completed and the stitch-forming mechanism has come to rest, the said stitchforming mechanism and the work-holding means will be given a relative movement to carry the parts from stitching position into buttonholecutting position thereby positioning the stitched buttonhole properly to be operated on by the buttonhole cutter. During this relative movement from stitching position to buttonhole-cutting position the thread or threads leading from the under side of the work, (which threads comprise the under thread and stay cord) are drawn through the throat plate.

In some buttonhole sewing machines the thread-trimming device which trims the thread underneath the work at the completion of the buttonhole is provided. with a thread-cutting edge situated and operating substantially in the plane of the under face of the work. A threadtrimming device for a buttonhole sewing machine of this type is shown in Patent No. 30 1,927,950 dated September 26, 1933.

In making buttonholes on some kinds of fabric it sometimes happens that the tension which is applied to the threads leading from the under side of the work as they are drawn through the throat plate by the movements of the parts from stitching position to buttonhole-cutting position applies a suificient downward pull on the work so that the operation of the thread trimmer is apt to injure either the last stitches of the button- 40 hole or the work.

One of the objects of the present invention is to provide improvements in thread-trimming devices of this type which will operate to separate the work from the cutting edge of the 45 thread cutter sufiiciently so that the thread may be trimmed close to the work without danger of cutting any of the threads of the buttonhole or injuring the work. This is provided for by posi- 50 tively-actuated means which operates after the work clamps have been opened but before the thread is cut to lift the work sufficiently above the cutter so that the latter may be actuated without any danger of injuring either the threads or the work and so as to place the threads in a more favorable position for the thread-trimming operation.

In the preferred embodiment of my invention the work-lifting element is actuated. by a cam carried on the main cam of the machine 5 and thus the work is lifted in perfect timed relation with the other operations of the sewing machine. Another object of the invention is to provide improvements in thread-trimming devices for sewing machines such as above de- 10 scribed which are constructed so that when the work is separated from the trimming devices, the thread will always be presented to the cutting edges of the trimming devices at the same angle regardless of the length of the buttonhole. 15

In order to give an understanding of the invention I have illustrated in the drawings a selected embodiment thereof which will now be described after which the novel features will be pointed out in the appended claims.

Fig. 1 is a side view of a portion of a button- 2 hole sewing machine embodying my invention;

Fig. 2 is a top plan view of the clamp plates of the machine removed therefrom and showing the work clamps and thread cutter;

Fig. 3 is a section on the line 3-3, Fig. 2;

Fig. 4 is an under side view of the clamp plates shown in Fig. 2 and illustrating the means for actuating the thread cutter;

Fig. 5 is a section on the line 5-5, Fig. 2;

Fig. 6 is a section on substantially the broken sectional line 6-6, Fig. 1 but showing the worklifting element in plan;

Fig. '7 is a section on substantially the line 1l, Fig. 2 and illustrating the position of the parts after the movement from stitching to buttonhole cutting position but before the clamps are opened;

Fig. 8 is a similar fragmentary sectional View illustrating the position of the parts after the clamps are opened and after the clamps have been raised;

Fig. 9 is also a similar fragmentary sectional view illustrating the position of the parts at the end of the stitching operation and before movement into buttonhole-cutting position;

Fig. 10 is a perspective view of the worklifting element;

Fig. 11 is a fragmentary perspective view showing a part of the connection for raising the work-lifting member;

Fig. 12 is a view of the cam which actuates the work-lifting member;

Fig. 13 is a view similar to Fig. 7 and illustrating the operation of the device in connection with a long buttonhole.

Fig. 14 is a fragmentary view similar to Fig. 13 but showing the work having a long buttonhole separated from the thread-trimming means and the thread to be trimmed presented to the trimming means.

Fig. 15 is a view similar to Fig. 13, but showing a short buttonhole.

Fig. 16 is a view similar to Fig. 14 except that a short buttonhole is shown.

The sewing machine shown in Fig. 1 is of that type which comprises a bed frame I carrying Work-holding means in which the work 2 is held during the sewing operation, and which also comprises a stitch frame 3 carrying the stitchforming mechanism, said stitch-forming mechanism having a feeding movement relative to the work-holding means during the sewing operation and a further relative movement after the stitch-forming mechanism comes to rest to carry the parts from stitching position to buttonholecutting position.

The work-holding means is mounted on the usual clamp plates 4 that are removably carried by the bed I. Said work-holding means includes the roughened plates or mats 5, t that are secured to the clamp plates 4, and clamping feet I, 8 which clamp the work against the mats 5 and B. These clamping feet are carried by clamp arms 9 pivoted to the clamp plates 4 at I!) as usual in buttonhole sewing machines of this type. The clamps I and 8 are operated by the usual mechanism which causes them to close onto the work before the sewing on the buttonhole begins and holds them clamped against the work during the sewing operation and which releases them at the completion of the sewing operation.

The stitch-forming mechanism is of the usual type which comprises a needle I I carried by the usual needle bar I2 which is reciprocated vertically in the head of the stitch frame 3 and whLch carries the needle thread I3, and loopers or their equivalent operating beneath the work and carried by the rotary turret I4 which is journalled in bearings I5, I6 formed in the lower portion I! of the stitch frame 3. This turret I4 carries at its upper end the usual throat plate 55 which is provided with the sewing opening I9 through which the needle I I operates and through which the under thread 20 and stay cord 2i are led to the sewing point.

Both the needle bar I2 and the turret I 4 are mounted for rotative movement for sewing around the end of the buttonhole as usual in buttonhole sewing machines.

The buttonhole cutter has the usual construction and comprises the two cutting elements 22, 23. The cutting element 22 is carried by a cutter lever 24 pivoted at 25 to the stitch frame 3 and said lever is actuated by a suitable cam projection (not shown) mounted on the main cam 26 which is located in the cam housing 27 that forms part of the stitch frame 3. The under buttonhole cutter member 23 is carried by the lower portion I! of the stitch frame 3.

The sewing machine herein shown is of that known type in which the necessary movement between the stitch-forming mechanism and Work-holding means is secured by a movement of the stitch frame 3 back and forth on the bed frame I and this movement is derived from the operation of the main cam 25 in a well-known way.

The parts are shown in full lines in Fig. 1 in the position they occupy at the end of the stitching operation on the buttonhole and the dotted lines show the position of the parts after they have been moved into buttonhole-cutting position, in which position the buttonhole cutter is placed properly for cutting the buttonhole slit.

During the movement from stitching position to buttonhole-cutting position the stitched buttonhole and the throat plate are separated from each other and lengths of under thread and stay cord are drawn through the throat plate. Fig. 9 shows the relative position of the work and the throat plate at the end of the stitching operation and Fig. 7 shows the relative position after the parts have been carried into buttonhole-cutting position.

The thread cutter herein illustrated is similar in many respects to that shown in Patent No. 1,927,950, dated September 26, 1933. Such thread cutter comprises two cutting elements 28, 29 which are coaxially pivoted on a stud 36 carried by one of the clamp plates 4. The cutting element 2% is in the form of a blade situated beneath the clamping foot 8 and having a cutting edge 3!, the upper face of this blade 29 being flush with the work-supporting face of the mat 6. Said mat 6 is cut away at its forward end to receive said blade when the latter is in inoperative position. The upper face of the blade 29 thus forms part of the work-supporting surface against which the work 2 is clamped by the clamping foot 8.

The thread-cutting member 28 is also in the form of a blade having a cutting edge 32 which normally extends transversely to the line of stitching when the thread cutting member is in its inoperative position.

Both of the blades are provided with central or hub portions through which the pivot Bil extends. The hub portion of the blade 28 is indicated at 33 and that of the blade 29 at 34. These two hub portions 33, 34 are superposed one on the other. The thread cutter is thus situated directly beneath the work and normally, or during the sewing operation, it is in contact with the under face of the work.

Each blade of the cutter is provided with a tail portion 35, and situated between said tail portions is a cam member 36 carried by a rock shaft 3'! journalled in one of the clamp plates 4. This rock shaft extends below the clamping plate and on its lower end it is provided with an arm 38 having a depending portion 39 that is adapted to be engaged by an upstanding arm 40 that is carried by the turret I4.

The rotation of the rock shaft 31 and the consequent turning movement of the cam 36 operates to spread the tails 35 of the cutter elements thereby closing the cutting edges 3I, 32 together, to perform the thread-trimming operation as described in said above-mentioned patent.

When the parts are being carried from stitching position to buttonhole-cutting position and the under thread and stay cord are being drawn through the throat plate the strain on the thread tends to pull the work down against the cutting blades and when operating on some kinds of work there is a danger that in their closing movement the cutting edges may injure either the threads of the buttonhole or the work. To prevent this we have provided herein a novel means for raising the work slightly from the work-supporting surface after the clamps I and 8 have been released and before the thread cutter is actuated, this raising movement of the work being sufficient to prevent any possibility of the thread trimmers injuring either the buttonhole stitches or the work. This lifting movement is accomplished through the operation of a positively-actuated work-lifting element, said element preferably deriving its work-lifting movement through the operation of a cam. This work-lifting element not only raises the work thereby separating it from the thread trimmers, but it also engages the thread extending from the last stitch to the throat plate l8 and places the thread in the same positionrelative to the trimming device regardless of the length of the buttonhole, which position is one that is favorable for trimming the threads accurately.

The work-lifting element is shown at 4| and in the present embodiment of the invention it is illustrated as a wire element having the horizontally-extending U-shaped portion 42 which is situated beneath the work just back of the sewing point. The two arms 43 of this wire member are secured to a head 44 that is mounted on the upper end of a vertically-moving rod 45. This rod is guided in bearings 45 carried on the end of a supporting arm 41 which is secured in the portion I! of the stitch frame. This arm 41 is shown as mounted on a pin or stud 48 which extends from one side to the other of the portion ll of the stitch frame as best seen in Fig. 6.

The work-lifting member 4| is normally held in its lowered or inoperative position, in which position the head 44 rests against the upper face of the portion H of the stitch frame as shown in Figs. 1 and 7, by means of a spring 49, which encircles the rod 45 below the lower bearing 46 and is confined between said bearings and a collar 50 on said rod. The head 44 thus provides a stop for limiting the spring-impelled move ment of the rod 45. In its lowered position the U shaped work-lifting element 4| is loctaed below the under face of the work as indicated in Figs. 7 and 9. When the rod 45 is raised in the bearings 46 against the action of the spring 49 such rising movement brings the portion 42 of the work-lifting member against the under side of the work and raises the work slightly from the work-supporting surface as shown in Fig. 8. This operation occurs after the clamps l and 8 have been released and by means of it the work is lifted sufficiently above the cutting edges of the thread cutters so that they can be operated without any danger of injuring either the buttonhole stitches or the work.

It will be noted that the work-engaging portion 42 of the work-lifting member 4| is on the buttonhole side of the throat when the stitchforming mechanism and work-holding means have moved relatively into the thread-trimming position, and that the relative movement of the parts from stitching position to thread-trimming position places the work-lifting portion 42 underneath the thread extending from the last stitch to the throat plate as shown in Fig. 7, and, therefore, when the work-lifting member is raised to lift the work as shown in Fig. 8, said member also acts on the threads 20, 2| and raises said threads as shown in Fig. 8 laying them across the cutting edge 32 of the cutter 28. The work-lifting member, therefore, lifts not only the work, but also the threads leading from the underside of the work.

Since the work-lifting member is carried by the portion I! of the stitch frame, it will have a fixed position relative to the throat in the direction of. the length of the buttonhole, and as a result of this construction the threadsleading from the underside of the work will always be presented to the trimmers at the same angle regardless of the length of the buttonhole, and hence the device herein illustrated will trim the threads of a short buttonhole as accurately as of a long buttonhole. This is shown best in Figs. 13 to 16.

In buttonhole sewing machines of this type the overall relative movement between the stitchforming mechanism and the work-holding means which takes place from the start of any buttonhole cycle to the sewing around the eye of the buttonhole is the same regardless of the length of the buttonhole. When the sewing machine is set in operation, the initial relative movement is from the starting position to a relative position at which the stitching on the buttonhole begins, and the continued relative movement is a feeding movement which takes place as the stitches are formed along one side of the buttonhole to the eye thereof and then back to the end of the buttonhole.

The length of the buttonhole is determined by the point in this relative movement at which the stitching begins. In the case of a relatively long buttonhole the stitching begins at a point in the relative movement nearer the starting position than in the case of a short buttonhole, and consequently when the stitching has been. completed and the parts have moved relatively into thread-trimming position, the amount of thread which is drawn through the throat and which extends from the last stitch to the throat at the time the threads are to be trimmed will be greater in the case of a short buttonhole than in the case of a long buttonhole.

With the present invention in which the worklifting member acts on both the work and the thread extending from the work to the throat and in which the work-lifting member has al fixed position relative to the throat plate in the direction of the length of the buttonhole, said work-lifting member will, during its rising or work-lifting movement, place the threads at the same angle to the cutting edge of the trimmer regardless of the length of the buttonhole. For

instance, in Figs. 13 and 14 there is shown the operation of the device in trimming the threads of a relatively long buttonhole H1, and. in 15 and 16 the operation of the device is shown when trimming the threads of a relatively short buttonhole 1|. buttonhole such as shown at 18 in Fig. 13, the length of the thread 20, 2| which extends from the finishing point 1.2 of the buttonhole to the throat after the'stitch-forming mechanism and work-holding means have moved relatively into their thread-trimming position, is less than the length of the thread extending from the end l3 of a short buttonhole 1| to said throat by an amount equal to the difference of length between the buttonholes. The work-lifting portion 42 of the work-lifting element, however, always has the same position relative to the throat in the direction of the length of the buttonhole, and after the parts have moved into the thread-trimming position shown in Figs. 13 to 16, the work-engaging portion 42 will always have the same position relative to the cutting edge 32 of the cutter 28 regardless of the length of the buttonhole. Consequently, when the worklifting member is raised to lift the work as In 'the case of a relatively long shown in Figs. 14 and 16, the closed or bridge portion end of the work-engaging portion 42 will act on the threads 26, 2| and lay them across the cutting edge 32 at the same angle whether the buttonhole is a long buttonhole or a short buttonhole. operate accurately to cut the thread regardless of the length of the buttonhole. This is clearly shown by comparing Figs. 14 and 16.

' This rising or operative movement of the worklifting member 4| is herein derived from a work-lifting cam 5| mounted on the main cam 26.

The supporting arm 4'! is provided with an extension 52 to which a lever 53 is pivoted at 54. The forward end of this lever is slotted as indicated at 55 to receive a stud or pin 68 extending from a block 56 through which the rod 45 extends and which is adjustably secured thereto. This block is held in adjusted position by means of a set screw 6|.

The rear or right hand end 5? of the lever 53 extends over the edge of the main cam 26 and into position to be acted on by the cam element 5|. This cam element 5| has the over-hanging cam face 58 and at the proper point in the rotation of the main cam 26 said cam face 58 rides over the end 51 of the lever 53 thereby depressing said end and raising the rod 45 and the work-lifting member 4|. As soon as the cam 58 has passed off from the end 51 of the lever 53 the spring 49 will return the work-lifting member to its normal or its inoperative position shown in Figs. 1 and '7.

The work-engaging portion 42 of the worklifting member 4| is shown as provided with a thread-receiving notch 59 in which the thread leading from the under side of the work is received when the work-lifting member is raised into its operative position shown in Fig. 8.

The construction herein shown is one which provides for raising the work to a greater or less extent. Under some conditions it may be suflicient to give the work a very slight lifting movement and under other conditions it may be desirable to give the work a greater lifting movement. This variation in the amount of lifting movement which the work receives is provided for by the adjustability of the block 56. The adjustment of the block 56 upwardly into a position above that shown in Fig. 1 will cause a lowering of the end 5! of the lever 53. Although the cam 5| has a fixed throw yet the amount which the cam depresses the end 5? of the lever 53 will depend upon the initial position of said end 51. If the block 55 is adjusted so as to place the end 51 below the position shown in Fig. 1 then when said end is engaged by the cam 5| said cam will give a lesser movement to the lever and conseouently a reduced rising movement to the worklift ng member. The work-lifting mechanism herein shown is also constructed so that it can be adjusted to vary the timing of the work-lifting movement with relation to the other operations of the machine. This is herein accomplished by constructing the work-lifting cam 5! so that its position on the main cam 26 may be adjusted thereby providing for variation of the point in the buttonhole sewing cycle at which the work is lifted or separated from the thread trimmers. As shown in Figs. 1 and 6 the cam 5| is provided with a foot portion 80 which is adjustably secured to the cam 26 through a clamping screw 8|. The foot 80 is provided with a slot 82 through which the clamping screw 8| extends The thread cutter will, therefore,

and this slot and screw provide means whereby the position of the work-lifting cam 5| on the main cam 26 may be shifted or adjusted. Any shifting of the position of the work-lifting cam 5| will cause a corresponding change in the timing of the operation of lifting the work, or, in other words, will produce a corresponding change in the point in the buttonhole cycle at which the work-lifting cam 5| functions to raise the work from the thread trimmer.

Our improvements, therefore, provide a positively-actuated or cam-actuated work-lifting member which is brought into action at the proper time in the buttonhole cycle to lift the work more or less above the thread-cutting element so that the latter may be actuated without any danger of injuring the buttonhole stitches or the work in which the buttonhole is formed.

The thread-trimming device herein shown is one in which the cutting edges are arranged substantially horizontally and have a relative cutting movement in a substantially horizontal plane. The length of thread and stay cord which are drawn through the throat plate at the end of the sewing operation by the shifting of the parts from stitching position to buttonhole cutting position lie very nearly parallel to the work. The raising of the work as above described not only carries said work and the buttonhole stitches above the cutters so as to eliminate the danger of injuring the work or the stitches by the cutting movement of the cutters, but such lifting movement also results in placing the threads extending from the under side of the work in a more favorable position for the thread-cutting operation. This lifting of the work gives the threads leading from the under side of the work a more nearly perpendicular position and carries said threads around the cutting edge of the cutting element 28 as shown best in Fig. 8.

We claim:

1. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means normally in contact with the under surface of the work, and means separate from the thread-trimming means to produce a relative separating movement between the work and the threadtrimming means just prior -to trimming the thread.

2. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means which clamp the work during the sewing and which release the work at th end of the sewing, thread-trimming means in; contact with the under surface of the work during the sewing, and means separate from the thread-trimming means to produce a relative separating movement between said thread-trimming means and the work after the sewing operation but before the threads are cut.

3. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means which clamp the work during the sewing and release the work at the end of the sewing, thread-trimming means in contact with the under surface of the work during the sewing, and means separate from the thread-trimming means to separate the work from the thread-trimming means after the clamps are released but before the thread is cut.

4. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means normally in contact with the under surface of the work, a main cam by which the operations of the machine are controlled, and means actuated directly by said cam to produce a relative separating movement between the work and the trimming means just prior to trimming the thread.

5. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means which clamp the work during the sewing and which release the work at the end of the sewing, a main cam controlling the opera- .tions of the machine, thread-trimming means in contact with the under surface of the work during the sewing, and means actuated directly by the main cam to produce a relative separating movement between said thread-trimming means and the work after the sewing operation but before the threads are cut.

6. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing of the buttonhole and which release the work at the end of the sewing, threadcutting mechanism operating beneath and in close proximity to the work, means to actuate the thread-cutting mechanism after the clamps have released the work, and means separate from the thread-cutting means and operating subsequent to the release of the clamps but before the thread is cut to separate the work from the thread-cutting mechanism.

7. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing of the buttonhole and which release the work at the end of the sewing, a main cam controlling the operations of the machine, thread-cutting mechanism operating beneath and in close proximity to the work, means to actuate the thread-cutting mechanism after the clamps have released the work, and means actuated directly by such main cam and operating subsequent to the release of the clamps but before the thread is cut to separate the work from the thread-cutting mechanism.

8. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing of the buttonhole and which release the work at the end of the sewing, threadcutting mechanism operating beneath and in close proximity to the work, means to actuate the thread-cutting mechanism after the clamps have released the work, and means independent from the thread-cutting mechanism and operating subsequent to the release of the clamps but before the thread is cut to raise the work from the thread-cutting mechanism.

9. In a buttonhole sewing machine, in combination, stitch-forming mechanism, Workclamping means which clamp the work during the sewing of the buttonhole and which release the work at the end of the sewing, thread-cutting mechanism operating beneath and in close proximity to the work, means to actuate the thread-cutting mechanism after the clamps have released the work, a main cam by which the operation of the machine is controlled, and means operated directly by the main cam subsequent to the release of the clamps but before the thread is cut to raise the work from the thread-cutting mechanism.

10. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing on the buttonhole and which release the work at the end of the sewing, a throat plate through which the thread is led to the work, said stitch-forming mechanism and workclamping means having a relative movement at the completion of the sewing to carry the parts from stitching position to button-holecutting position and to draw out a length of thread through the throat plate, a main cam by which the operations of the machine are controlled, a thread cutter for cutting the thread between the throat plate and the last stitch, means to actuate the thread cutter after the clamps are released, and means independent from the thread cutter and a cam element carried by the main cam to separate the Work from the cutter prior to the cutting of the thread.

11. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means operating beneath the work, a work-lifting cam, adjustable means actuated thereby to raise the work relative to the thread-trimming means, the adjustability of said adjustable means providing for raising the work to a greater or less extent.

12. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means operating below the work, a work-lifting member, a work-lifting cam having a fixed throw, connections between said cam and said work-lifting member, whereby the latter is raised by the operation of said cam, said connections being adjustable to provide for varying the extent of the work-lifting movement of the work-lifting member.

13. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing on a buttonhole and which release the work at the end of the sewing, a throat plate through which the thread is led to the under side of the work and which is separated from the stitched buttonhole at the end of the sewing, thread-trimming means situated beneath the work, a main cam by which the operations of the machine are controlled, a cam element carried by the main cam, and means independent from the trimming mechanism and actuated by said cam element to separate the work from the trimming means after the clamps are released thereby to place the thread leading from the work to the throat plate at a more favorable angle for the thread-trimming operation.

14. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means which clamp the work during the sewing and release the work at the end of the sewing, a throat plate through which the thread is led to the under side of the work, and which is separated from the stitched buttonhole at the end of the sewing, thereby causing a length of thread to be drawn therethrough, thread-trimming means having a cutting edge movable in a substantially horizontal plane, a main cam by which the operations of the machine are controlled, a cam element carried by the main cam, and means independent from the trimming mechanism and actuated by said cam element to separate the work and the trimming means after the clamps are released thereby to carry the thread around said cutting edge.

15; In a buttonhole sewing machine, in combination, stitch-forming mechanism, threadtrimming means operating beneath the work, a work-lifting cam, means actuated thereby to separate the work from the thread-trimming means, said cam being adjustable to vary the timing of the work-separating movement.

16. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means operating beneath the work, a main cam by which the operation of the machine is controlled, a work-lifting cam carried by the main cam, and means actuated by the work-lifting cam to separate the work from the thread-trimming means prior to the operation of the latter.

17. In a buttonhole sewing machine, in combination, stitch-forming mechanism, workclamping means, thread-trimming means operating beneath the work, a main cam by which the operations of the machine are controlled, a work-lifting cam carried by the main cam, adjustable means actuated by the work-lifting cam to separate the work from the thread-trimming means prior to the thread-trimming operation, the adjustability of said adjustable means providing for separating the work from the threadtrimming means to a greater or less extent.

18. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means, thread-trimming means operating beneath the work, a main cam by which the operations of the machine are controlled, a worklifting cam adjustably carried by the main cam, and adjustable means actuated by said worklifting cam to separate the work from the thread-trimming means prior to the operation of the latter.

19. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means, thread-trimming means operating beneath the work, a main cam by which the operations of the machine are controlled, a worklifting cam adjustably carried by the main cam, and means actuated by said work-lifting cam to separate the work from the thread-trimming means prior to the operation of the latter.

20. In a buttonhole sewing machine, in combination, stitch-forming mechanism, work-clamping means, thread-trimming means operating beneath the work, a work-lifting member, a lever for actuating said member, a work-lifting cam for giving operative movement to said lever, and an adjustment for the lever by which the extent of operative movement given thereto by the work-lifting cam may be varied.

21. A buttonhole sewing machine having stitch forming mechanism work clamping means, a throat through which the threads are led to the underside of the work, thread-trimming means having a cutting edge and operating beneath the work, and means operative at the end of the sewing on a buttonhole to engage both the under face of the work and the threads leading from the work to the throat at a point between the last stitch and the throat and to cause a separation of the work from the threadtrimming means and also to present the thread to the trimming means.

22. A buttonhole sewing machine having stitch forming mechanism, work clamping means, a throat through which the threads are led to the underside of the work, thread-trimming means having a cutting edge and operating beneath the work, and means operative at the end of the sewing on a button hole to engage both the under face of the work and the threads leading from the work to the threat at a point between the last stitch and the throat and to cause a separation of the work from the threadtrimming means and also to lay the thread across the edge of the trimming means.

23. A buttonhole sewing machine having stitch forming mechanism, work clamping means, a throat through which the threads are led to the underside of the work, thread-trimming means having a cutting edge and operating beneath the work and means operative at the end of the sewing on a buttonhole to engage both the under face of the work and the threads leading from the work to the throat at a point between the last stitch and the throat and to cause a separation of the work from the threadtrimming means and also to lay the thread across the edge of the trimming means at a given angle regardless of the length of the buttonhole.

24. A buttonhole sewing machine having stitch forming mechanism, work clamping means, a throat plate through which the thread is led to the underside of the work, said stitchforming mechanism and work-clamping means having a relative movement at the completion of the sewing by which a length of thread is drawn through the throat plate, thread trimming means, a work-lifting member which is placed beneath the work and the threads leading therefrom to the throat by said relative movement and means to raise the work-lifting member thereby to cause it to engage both the work and the threads and to separate the work from the trimming means and to place the thread at a more favorable angle for the thread trimming operation.

25. A buttonhole sewing machine having stitchiorming mechanism, work-clamping means, a throat plate through which the thread is led to the underside of the work, said stitch-forming mechanism and work-clamping means having a relative movement at the completion of the sewing by which a length of thread is drawn through the throat plate, thread trimming means a work-lifting member having a fixed position relative to the throat in the direction of the length of the buttonhole and means to raise the work-lifting member after the completion of said relative movement, thereby to separate the work from the trimming means.

26. A buttonhole sewing machine having stitchforming mechanism, work-clamping means, a throat plate through which the thread is led to the underside of the work, said stitch-form ing mechanism and work-clamping means having a relative movement at the completion of the sewing by which a length of thread is drawn through the throat plate, thread trimming means, a work-lifting member having a fixed position relative to the throat in the direction of the length of the buttonhole and situated on the buttonhole side of said throat at the end of said relative movement, and means to raise the Work-lifting member thereby to separate the work from the trimming means.

27. A buttonhole sewing machine having stitchforming mechanism, work-clamping means, a throat plate through which the thread is led to the underside of the work, said stitch-forming mechanism and Work-clamping means having a relative movement at the completion of the sewing by which a length of thread is drawn through the throat plate, thread trimming mechanism, a work-lifting member separate from the work clamps and having a fixed position relative to the threat in the direction of the length of the buttonhole, and means to raise the worklifting member to separate the work from the trimming means.

28. A buttonhole sewing machine having means for sewing buttonholes of varying lengths, a thread trimmer having a cutting edge to trim the thread after the sewing on any buttonhole is completed and means operative regardless of the length of the buttonhole to present the thread to the cutting edge at the same angle for being cut.

29. A buttonhole sewing machine for sewing buttonholes of varying lengths comprising stitchforming mechanism and work-holding means movable relative to each other for sewing the buttonhole and, when the machine comes to rest at the conclusion of each buttonhole cycle having the same relative position for all lengths of buttonholes, thread-trimming means naving a cutting edge and means to present the thread to said edge at substantially the same angle for trimming regardless of the position of the last stitch of the buttonhole relative to the stop position of the stitch-forming mechanism.

30. A buttonhole sewing machine having means for sewing buttonholes of varying lengths, a thread trimmer having a cutting edge to trim the thread after the sewing on any buttonhole is completed and means to engage the thread between the sewed buttonhole and the thread trimmer to present the thread to said cutting edge at a favorable angle for being cut.

31. A buttonhole sewing machine having stitchforming mechanism, work-clamping means, thread trimming means having a cutting edge and operating beneath the work and means operative at the end of a sewing on a buttonhole to engage the thread leading from the work at a point between the sewed buttonhole and the said cutting edge and to present said thread to said cutting edge at a favorable angle for being cut.

M332. A buttonhole sewing machine having stitchforming mechanism, work-clamping means, a throat through which the threads are led to the under side of the work, thread trimming means having a cutting edge and operating beneath the work and means operative at the end of a sewing on a buttonhole to engage both the under face of the work and the threads leading from the work to the throat at a point between the last stitch and said cutting edge and to cause a separation of the work from the trimming means and also to present the thread to the trimming means.

JOSEPH H. PIKUL. CARL A. O. GRIP. 

